The image can also be shrunk even futher using the
minimize_size plugin.
With optimal settings a 64-bit jessie image can be whittled down to 81.95 MB
(built on Dec 13th 2015 with manifests/examples/docker/jessie-minimized.yml).

dockerfile: List of Dockerfile instructions that should be appended to
the ones created by the bootstrapper.
optional

labels: Labels that should be added to the dockerfile.
The image name specified at the top of the manifest
will be added as the label name.
Check out the docker docs
for more information about custom labels.
Project atomic
also has some useful recommendations
for generic container labels.
optionalmanifestvars